The propagation of hepatitis A virus in cell culture in vitro has been described by Provost et al., Proc. Soc. Exp. Biol. Med. 160, 213-221 (1979), and also in U.S. Pat. No. 4,164,566. In these prior art techniques, however, the infected cells are disrupted to harvest the virus and the virus is then used to infect a new culture of uninfected cells in vitro.